Neptune is the eighth and farthest known planet from the Sun in the Solar System. In our Solar System it is the fourth largest planet by diameter, the third most massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth, slightly more massive than its near twin Uranus.
Neptune is denser and physically smaller than Uranus because its greater mass causes more gravitational compression of its atmosphere. It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune’s trident.
With a radius of 15,299.4 miles (24,622 kilometers), Neptune is about four times wider than Earth.
From an average distance of 2.8 billion miles (4.5 billion kilometers), Neptune is 30 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 4 hours to travel from the Sun to Neptune
One day on Neptune takes about 16 hours. And Neptune makes a complete orbit around the Sun in about 165 Earth years.